Polyorganosiloxanes (silicones) of a condensation reaction type that cure at room temperature to produce rubbery elastic bodies are in wide use as an elastic adhesive, a coating material, an electrically insulating sealing material, and the like in the electric and electronic industry and also as a building sealing material.
Among them, polyorganosiloxane of a single-component type (single-package type) which undergoes a curing reaction when coming into contact with water in the air is easy to handle because there is no need for a troublesome work of weighing and mixing a base polymer and a cross-linking agent, a catalyst, and so on immediately before it is used, but it has disadvantages of a slow curing speed and poor deep-part curability.
On the other hand, room temperature-curable polyorganosiloxane of a two-component type is high in curing speed and excellent in deep-part curability. In preparing this composition, a base component composed of: polydiorganosiloxane having molecular ends capped with hydroxyl groups and/or alkoxy groups; and an inorganic filler is separately prepared from a cross-linking component. They are preserved in separate containers and mixed when in use, that is, this composition is used as what is called a multi-package-type room temperature-curable composition (refer to JP-A Hei 7-133430 (KOKAI), JP-A Hei 11-209620 (KOKAI), for example).
However, in such room temperature-curable polyorganosiloxane of the two-component type, since the cross-linking component is composed only of a cross-linking agent and a curing catalyst in view of storage stability, a compounding ratio of the cross-linking component to the base component is very small such as 1 to 3 mass %, which is likely to cause wide variation in quantity at the time of measurement and poor mixing.
Especially in the mixing using an automatic mixer/discharger, in a practical point of view, a mixing ratio of the base component and the cross-linking component is required to be about 100:10, or an integer ratio where the ratio of the cross-linking component is equal to or more than the aforesaid ratio, but for a conventional silicone rubber of the two-component type whose cross-linking component is composed only of the cross-linking agent and the curing catalyst, the measurement without any variation has been difficult.
In the case where the automatic mixer/discharger is used for the measurement and mixture, in order to increase a mixing ratio of the cross-linking component, it is conceivable that the same polymer as a base polymer (for example, silanol group-terminated polydiorganosiloxane) in the base component is blended as an extender also in the cross-linking component. However, such a two-component-type composition has problems of not only deterioration of storage stability of the cross-linking component due to the coexistence of the base polymer, the cross-linking agent, and the catalyst in the cross-linking component but also the separation of the base polymer and the cross-linking agent due to their poor compatibility.